use warnings rather than logging a warning for DecimalField warnings (#9367)

rest_framework/fields.py

@@ -4,9 +4,9 @@ import datetime
 import decimal
 import functools
 import inspect
-import logging
 import re
 import uuid
+import warnings
 from collections.abc import Mapping
 from enum import Enum
 
@@ -44,8 +44,6 @@ from rest_framework.utils.formatting import lazy_format
 from rest_framework.utils.timezone import valid_datetime
 from rest_framework.validators import ProhibitSurrogateCharactersValidator
 
-logger = logging.getLogger("rest_framework.fields")
-
 
 class empty:
     """
@@ -989,9 +987,9 @@ class DecimalField(Field):
         self.min_value = min_value
 
         if self.max_value is not None and not isinstance(self.max_value, decimal.Decimal):
-            logger.warning("max_value in DecimalField should be Decimal type.")
+            warnings.warn("max_value should be a Decimal instance.")
         if self.min_value is not None and not isinstance(self.min_value, decimal.Decimal):
-            logger.warning("min_value in DecimalField should be Decimal type.")
+            warnings.warn("min_value should be a Decimal instance.")
 
         if self.max_digits is not None and self.decimal_places is not None:
             self.max_whole_digits = self.max_digits - self.decimal_places

tests/test_fields.py

@@ -4,6 +4,7 @@ import os
 import re
 import sys
 import uuid
+import warnings
 from decimal import ROUND_DOWN, ROUND_UP, Decimal
 from enum import auto
 from unittest.mock import patch
@@ -1254,15 +1255,19 @@ class TestMinMaxDecimalField(FieldValues):
     )
 
     def test_warning_when_not_decimal_types(self, caplog):
-        import logging
-        serializers.DecimalField(
-            max_digits=3, decimal_places=1,
-            min_value=10, max_value=20
-        )
-        assert caplog.record_tuples == [
-            ("rest_framework.fields", logging.WARNING, "max_value in DecimalField should be Decimal type."),
-            ("rest_framework.fields", logging.WARNING, "min_value in DecimalField should be Decimal type.")
-        ]
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter('always')
+
+            serializers.DecimalField(
+                max_digits=3, decimal_places=1,
+                min_value=10, max_value=20
+            )
+
+            assert len(w) == 2
+            assert all(issubclass(i.category, UserWarning) for i in w)
+
+            assert 'max_value should be a Decimal instance' in str(w[0].message)
+            assert 'min_value should be a Decimal instance' in str(w[1].message)
 
 
 class TestAllowEmptyStrDecimalFieldWithValidators(FieldValues):